Renewable energyis energy derived from a renewable or replenishable resource. Sources include sunlight or solar energy, and others such as wind, wave, tidal, biomass and hydro energy. Diagram S15.1 shows the sun as the origin of these renewable energy resources and their potential to be converted to electricity. Geothermal resources are derived from such a large energy source that the rate of depletion is negligible, and are therefore also regarded as renewable.

Two main reasons for renewable energy's rapid growth are the depletion of fossil and other non-renewable fuels, and concerns about the effects of greenhouse gas emissions. As well as being perpetually available, renewable energy sources are low polluting and produce very little or no net greenhouse gas emissions when operating. In Australia, government, industry and community support are driving renewable energy growth, particularly for electricity generation and transport use.

Although depletion of fossil fuels is far from being an issue for Australia, there are many environmental benefits to be gained from renewable energy development. However, there are potential negative as well as positive environmental impacts, specific to each renewable energy source. Careful planning and use of appropriate existing or new technologies may overcome many of the potential problems and so maximise the potential benefits.

S15.1 SOLAR ENERGY CONVERSION PATHS

Renewable energy's role in sustainable energy development and greenhouse gas emissions reduction

Renewable energy, energy efficiency and use of cleaner fossil fuel technologies are key tools in a strategy for sustainable energy use and greenhouse gas emissions reduction. Energy use in Australia continues to rise due to economic development, an increasing number of energy intensive industries, population growth and rising standards of living that increase demand for energy and for energy intensive products. About 94% of domestic energy use comes from fossil fuels and the rest from renewable energy (ABARE 2001).

The structure of the Australian economy, and its heavy reliance on fossil fuels for its energy, translates to high emissions of carbon dioxide, the main greenhouse gas contributing to global warming. The energy sector accounted for 362.6 million tonnes (Mt) or 79.6% of total net national greenhouse gas emissions in 1999, an increase of 1.0% from 1998 and 21.7% from 1990. This compares with the total net national emissions increase of 17.4% (excluding land clearing) from 1990. Emissions associated with land clearing have decreased significantly since 1990. As a result, once emissions associated with land clearing are included in Australia’s national greenhouse gas inventory, the overall growth in emissions since 1990 is expected to be significantly less than 17%. The Kyoto Protocol target for Australia restricts emissions to a maximum of 8% by the budget period 2008-12 (AGO 2001).

Within the energy sector, electricity generation and transport are the biggest energy consumers and contributed 37.5% and 16.1% respectively to total net national greenhouse emissions in 1999. This points to a need to increase renewable energy for electricity generation and transport as an effective means for Australia to constrain the growth in its greenhouse emissions.

The relatively low cost of fossil fuels has been a constraint on investment in renewable energy, and correspondingly there is currently a price premium attached to the use of renewable energy. Table S15.2 shows estimates of unit costs of electricity generation in 1998-99 by fuel type and gives an indication of this price premium (ABARE 2001). However there is mounting support for renewable energy from governments, industries and households.

S15.2 UNIT COSTS OF ELECTRICITY GENERATION - 1998-99

Cost of existing power plants

Cost of new power plants

Fuel type

$ per ‘000 kWh

$ per ‘000 kWh

Black and brown coal, natural gas

32.66 - 36.04

30.11 - 32.70

Hydro-electricity

43.13

41.76

Wind energy

56.62

50.83

Biomass (including biogas)

108.53 - 122.88

46.87 - 60.32

Source: ABARE 2001.

Support for renewable energy

Commonwealth Government

A range of Commonwealth government initiatives and funding of $381m are in place to boost the uptake of renewable energy. These are part of the measures announced in the 1997 Climate Change Statement ($60m over five years) and the 1999 Measures for a Better Environment ($321m over four years). The majority of the funding was for power generation using renewable energy especially for remote areas, but there were small measures to assist the development of transport fuels from renewable sources. Additionally, in early 2002, the Australian Government announced a $50m bio-fuels initiative to enable renewable fuels such as ethanol to provide 2% of the country's transport fuel.

Among these government initiatives, the most significant market driver is the Mandatory Renewable Energy Target (MRET). The MRET places a legal requirement on electricity wholesalers and large energy users to purchase an additional quantity of electricity generated from renewable sources. In order to improve planning certainty, the requirement is for an additional 9,500 gigawatt hours (GWh) of renewable generation by 2010. The measure is phased in via a number of interim targets over the period 2001-2010, and the final 9,500 GWh target must be maintained between 2011 and 2020 (http://www.orer.gov.au). The measure applies nationally. All wholesale electricity buyers and retailers on grids of over 100 megawatts (MW) capacity in all states and territories must contribute to the measure.

In order to discharge their renewable energy liability, liable parties (electricity retailers or large energy users) must surrender an assigned number of Renewable Energy Certificates (RECs) to the Office of the Renewable Energy Regulator (ORER). The requirement to purchase renewable electricity is determined by the ORER and allocated in proportion to the overall electricity purchases of liable parties.

RECs are generated by the production of renewable energy. Each megawatt hour (MWh) of electricity generated from an eligible renewable energy source creates one REC. The ORER issues the RECs to renewable generators - one REC for each MWh generated. New renewable generators obtain RECs for their entire output, whereas existing generators (mostly large hydro) receive RECs for generation above a base line set on 1997 production. Renewable generators can then sell their RECs to liable parties in order to discharge this liability. The purchasers’ liability under the MRET for any year is met when they surrender the required number of certificates to the regulator.

There is no option available to 'sign up', as the target is mandatory and a legal obligation on the part of liable parties is legislated. A penalty of $40/MWh is payable for each REC not purchased, effectively setting a price cap on compliance and capping the cost of the subsidy to electricity consumers.

RECs are traded on the Green Electricity market developed by the Australian electricity industry. Over 600,000 RECs were created in 2001, providing more than enough certificates to cover MRET's first year target of 300,000 RECs and a head start for 2002's larger target of 1.1 million RECs. Contributions to the 2001 target of 300,000 RECs from different renewable sources are shown in graph S15.3. This shows that wind and landfill gas, which were previously used in negligible amounts, could experience strong growth under the MRET scheme.

State, territory and local governments

Through participation in Commonwealth government programs and their own initiatives, state, territory and local governments are actively promoting renewable energy and assisting industries in the commercialisation and use of sustainable energy technologies. For example, New South Wales imposes mandatory reduction targets on its privatised electricity industry through the Electricity Supply Act 1995 (NSW), and in mid 2002 the Victorian Government announced the Victorian Greenhouse Strategy, promising 59 actions to combat greenhouse gas emissions. Many initiatives involve providing information, guidelines and other practical help. As an example, the development of wind energy in New South Wales is aided by a Wind Monitoring Network set up by the New South Wales Sustainable Energy Development Authority (SEDA). This network incorporates twenty-five 40-metre monitoring towers across the state. A New South Wales wind atlas of the state's wind resource, based on data from these towers and other sources, is also available to the public.

Industry and R&D

The Renewable Energy Industry Action Agenda, launched in June 2000, was established by the Department of Industry, Tourism and Resources to build a partnership between industry and government to fast-track the growth of the industry. It aims to achieve annual sales of $4b of renewable energy technologies by 2010 (DISR 2000). Industry has identified many action points including the need to deliver products and services that provide cost effective and reliable 'energy solutions' to customers. A technology roadmap for the renewable energy industry has been developed to encourage greater collaboration between industry and the research community. Standards, training and accreditation initiatives are being developed to support improvement to product and service quality and reliability. There is general recognition that renewable energy has enormous growth potential and that export opportunities are the key to achieving economies of scale, which are important in lowering the cost of renewable energy.

Households

Households can directly contribute to the increased use of renewable energy for electricity generation through the Green Power program administered by SEDA. This is a national accreditation program that sets stringent environmental and reporting standards for renewable energy products offered by electricity suppliers across Australia. More than 55,000 households (and about 2,500 businesses or local councils) are customers of Green Power. By asking energy suppliers to provide them with electricity generated from renewable sources, these customers voluntarily pay a higher price for their electricity to support the use of renewable energy. An average home that has subscribed to 100% Green Power (including off-peak) is estimated to save eight tonnes of carbon dioxide annually, equivalent to taking just over two cars off the road. SEDA's National Green Power Audit showed that the total green energy sales increased by 50% from the previous year to reach 455 GWh in 2000-01. Over the four-year life of the Green Power program, demand for genuine renewable energy has increased tenfold from 40 GWh in 1997.

Renewable energy growth

The growing support for sustainable energy, including renewables, has yielded measurable results. Electricity generation increased by 4% from 1997-98 to 1998-99 while electricity emissions increased by 1.9%, an indication that a greater proportion of lower emission fuels, or cleaner fuel technologies, were used during 1998-99 to produce electricity. By contrast, in the previous year electricity generation increased by 6% and emissions increased by more than 10%.

In 1999, the Australian Bureau of Agricultural and Resources Economics estimated that the 6% of total primary energy that came from renewable energy was largely from biomass in the form of bagasse (39%) which was used to generate electricity and steam, wood (39%) which was used primarily for home heating, hydro-electricity (21%) and solar (1%). Renewable energy contributed 11% to electricity generation, most of which was generated from large-scale hydro-electric schemes (ABARE 1999).

Environmental considerations in developing renewable energy

Australia is well endowed with renewable energy and is an international leader in a number of technologies, such as R&D for photovoltaic modules and fuel cells, solar thermal and remote area power systems. Momentum for renewable energy development in Australia is gaining rapidly due to the urgent need to stabilise greenhouse gas emissions. Large potential economic and social benefits are also expected to flow from renewable energy development. Among the economic benefits, particularly to rural and remote areas, are: cost-effective clean energy; renewable energy industry and market creation; R&D development; and export potential. Renewable energy facilities can be built near customers to reduce energy losses in electricity transmission, a particular advantage in transmission lines feeding rural areas. Availability of low-cost, clean and reliable energy, improved land, air and water quality, and job creation have positive impacts on people's health and wellbeing.

There are other environmental effects, negative as well as positive, specific to each type of renewable energy resource/technology. They include effects on air, water and soil quality; impact on biodiversity, flora and fauna; and noise and visual impact. Careful assessment of these impacts and the adoption of environmentally sound technologies and practices are an essential part of planning for renewable energy projects and their implementation. The remainder of this article discusses these environmental effects as they relate to different renewable energy resources, and presents case studies.

Hydropower

Hydropower is produced by the movement of freshwater from rivers and lakes. The most common form of hydropower plant uses a dam on a river to store water in a reservoir. Enormous quantities of water are involved and a large hydro-electric power system requires a very large dam, or a series of dams. In Australia hydropower is currently the largest source of renewable energy for electricity generation (over 8% of total supply) and is expected to retain this position, although its share is projected to drop to about 6% by 2019-2020 (ABARE 2001). Most of this hydropower is from the two largest plants, the Snowy Mountains scheme and the Tasmanian Hydro-Electric installation.

Although it is a renewable energy source, hydropower does carry a greenhouse gas penalty due to the production of methane, which arises from the rotting of underwater vegetation. The extent to which methane is produced in a hydro-electric dam depends on a variety of factors, including the original vegetation on the dam site, water temperature, and the area of the dam. Shallow warm tropical dams are more likely to be major emitters of methane than deep cold dams located in temperate regions. Recent studies from the Australian Coal Association Research Program on power generation in Brazil led the Commonwealth Scientific and Industrial Research Organisation to assign a greenhouse gas production value of 0.19 tonnes of carbon dioxide equivalent (CO2-e) to each MWh of hydro-produced electricity. This is about one-third of the value assigned for electricity produced using natural gas and one-fifth the amount allocated to power stations burning black coal.

Fish injury and mortality from passage through turbines and detrimental effects on the quality of downstream water (hydro can cause low dissolved oxygen levels in the water which is harmful to riparian habitats) are also potential negative environmental effects of hydropower. Mitigating techniques are available, for example, upstream fish passage can be aided usingfish laddersor elevators, and maintaining minimum flows of water downstream helps the survival of riparian habitats. An important determinant of environmental impacts is the size of hydropower plants, which ranges from micro to large.

Large-scale hydro is associated with significant negative environmental impacts, including detrimental effects on river flows and water supplies. The flooding of large areas of land often leads to the displacement of local residents and negative impacts on local fauna and flora. The 500 MW Tully Millstream project was shelved due to the potential inundation of a World Heritage rainforest.

Smaller hydro systems do not experience these problems, or experience them to a much lesser extent. In particular, micro hydro systems (less than 100 kilowatts (kW)) are preferable from an environmental point of view. Seasonal river flow patterns downstream are not affected and there is no flooding of valleys upstream. These systems operate by diverting part of the river flow through a penstock (or pipe) and a turbine, which drives a generator to produce electricity. The water then flows back into the river. Micro hydro systems are mostly 'run of the river' systems which allow the river flow to continue. They provide an attractive alternative or supplement to diesel systems in rural and remote areas.

Case studies

Mini hydro case study (Australian Energy News, December 2000)

The construction of a very cost effective mini hydro generator on the 11,000 megalitre Toonumbar Dam near Lismore in the north of New South Wales resulted from a 1998 study commissioned by SEDA which identified the potential to develop or upgrade hydro-electric plants on 32 dams in New South Wales. Toonumbar is an irrigation dam, and the generator runs only when water is released or when the dam is overflowing. It has a capacity to produce 400 MWh of hydro-electricity a year. The proximity to regional and rural electricity loads is a great advantage and transmission losses are minimised when power does not need to be transported over long distances.

The hydro is constructed on an existing dam, the Pindari Dam near Ashford, Inverell in northern New South Wales. The dam is primarily used for irrigation purposes and has a storage capacity of 312,000 megalitres. The irrigation releases provide the means of generating electricity. The project is a small hydro (defined as having a size of 1 MW to 10 MW) construction with two horizontal Francis turbines rated at 2.8 MW each. The plant's long-term average energy output is estimated at about 16,300 MWh per annum, enough to supply approximately 4,000 households. The power is exported to the national grid via an 8 km 66 kilovolt transmission line. The project is expected to save 14,600 tonnes of CO2-e per year during its 80-year lifetime.

Biomass

Biomass is derived from plant and animal material, and can be used in a variety of ways to supply energy (heat, electricity, liquid and gas fuels, charcoal) and various chemicals and other products. Sources of biomass fall into five main groups: wood and forest; agricultural residues; energy crops and short rotation forests; municipal and industrial wastes; and peat. A considerable biomass resource exists in Australia including woody weeds, field crop residues, bagasse from large sugar mills, cotton and rice residues, residues from large forest and plantation operations (eucalypts and radiata pine), waste from sawmills and the pulp and paper industry, and landfill gas.

The potential of biomass to supply energy and reduce greenhouse gas emissions is large. On a world scale the International Energy Agency estimates that biomass energy sources have the potential to meet 40% of all present energy consumption. It has been estimated that, if biomass was to contribute 1,000 MW of Australia's electricity generating capacity, net carbon dioxide emissions would fall by about 7.4 Mt a year.

There are many environmental benefits as well as negative impacts from the use of biomass. Relative to other renewable energy sources, the much wider range of environmental effects associated with biomass reflects the large variety of biomass sources, conversion processes and products.

Additional environmental benefits offered by biomass are many, the major one being in solving waste disposal problems. By far the greatest source of feedstocks for biomass-to-energy schemes is by-products of existing agricultural, industrial and urban processes. Recycling, combined with advanced waste-to-energy combustion or gasification, reduces the need for landfill disposal. A follow-on benefit can be reduced problems with waste leaching into groundwater. Decaying of waste in landfills produces methane, the emission of which has higher global warming potential than carbon dioxide. It has been estimated that one tonne of methane from ruminant enteric fermentation has 21 times the global warming potential of one tonne of carbon dioxide over a 100-year period. Similarly, nitrous oxide released from animal wastes is 310 times as potent as carbon dioxide.

Processing of biomass can lead to improvement to the local environment (odour control, air and water quality). Treating waste in an anaerobic digester, rather than allowing it to decay naturally, improves local air quality. The biogas piped off is a valuable energy source, and the waste is substantially sterilised. Digestion of animal manure kills pathogens; the residue can then be spread safely as an agricultural fertiliser. Sewerage effluent treatment prior to discharge to waterways or oceans improves water quality. Unlike coal and oil, biomass contains no sulphur, or negligible quantities; sulphur is the main cause of acid rain.

Biomass can play a significant role in land care. Trees planted for energy can assist with the reduction of soil salinity and acidity, and the mitigation of soil erosion, the use of wastewater, the sequestration of atmospheric carbon and enhanced biodiversity. The ash left after combustion of most biomass contains negligible amounts of toxic metals, and so can be used as a soil conditioner.

Biofuels can be used for transport fuels. Other renewable energy sources could potentially be used to produce hydrogen or electricity for use in motor vehicles, although these applications are far from being economic or available for general use yet.

On the other hand, there are many more issues to be considered in the assessment of biomass projects than those for other sources of renewable energy. This is in part due to the variety of biomass material available as well issues associated with its use. If biomass resources are to be maintained on a sustainable basis, it will be important to ensure that the rate of harvesting of these resources does not exceed the rate at which they are grown. It will also be necessary to ensure that the use of biomass resources does not adversely impact on biodiversity.

Sawdust and wood waste make sawmills a very attractive site for biomass-to-energy investment. Not only are large sites producing thousands of tonnes of material a year that would otherwise produce methane and carbon dioxide as it decomposed or burned, but the sawmills are also substantial users of electricity and in some cases process heat as well. These conditions make biomass-to-energy investments at large sawmills a likely part of any energy sector response to greenhouse gas reduction.

However, using waste for energy purposes could reduce the desirable incentives to minimise and recycle waste materials, if it is cheaper to burn it. Stack emissions from municipal solid waste-to-energy plants, and also possibly from wood-fired biomass plants, could contain toxic substances such as dioxins which would need to be controlled.

Other issues centre around the life-cycle costs and benefitsof the energy material: how was it produced and manufactured - what is the ecological footprint of the demand created by the bio-energy companies? Does the material have a higher beneficial use than simply a one-off energy exercise? Could it be better used to replace other virgin materials? Also, transport of large quantities of biomass to the power plants would result in increased traffic congestion, noise, dust, road damage and fuel use.

Other concerns surround the growing of 'energy crops'. Planting large areas with fast growing trees could reduce both water run-off and percolation into the groundwater, impacting on downstream users. Biodiversity could be further threatened and agri-chemical use could be increased. Soil nutrient levels could be depleted by continually removing large quantities of biomass material such as crop residues from the land. There is concern among some sections of the community that genetically engineered trees and crops could be developed specifically for use for bio-energy supplies. The use of land for energy cropping could reduce the area of land otherwise available for food and fibre production, resulting in land scarcity.

This Sydney water cogeneration project forms part of an upgrade of the Cronulla Sewerage Treatment Plant. Sewerage wastewater, when treated anaerobically (oxygen excluded), produces methane that in this project is collected and used to generate renewable power. Otherwise the methane would either be flared or vented to the atmosphere with adverse environmental impacts. Methane has 21 times the greenhouse gas impact of carbon dioxide.

The power produced by the biogas generation project displaces purchases of high value electricity from the grid. The unit produces about 2,470 MWh of power per year - approximately 10% of the power requirements of the Cronulla Treatment Plant. The heat produced by the engine exhaust and jacket is recovered and used to heat the sewerage sludge in the anaerobic digestion process, which assists the processing of the sludge and the production of the methane for the generation unit. The biogas cogeneration plant is designed to use 100% of the gas produced by the digesters and can be operated 24 hours a day, 7 days a week.

Producing power 'on site' increases the reliability of supply to the plant. The plant reduces greenhouse gas emissions arising from the processing of Cronulla's sewerage by 17,000 tonnes of carbon dioxide each year.

Construction of Anaerobic Digester at Camellia, New South Wales (Bioenergy Australia Newsletter, April 2002)

EarthPower Technologies Sydney, in association with Babcock and Brown and contractor McConnell Dowell Constructors (Aust) Pty Ltd, is constructing a state-of-the-art anaerobic digester at Camellia in Sydney’s western suburbs.

The $30m facility will process food wastes and food processing wastes to produce 7 MW equivalent of methane gas and high nutrient organic fertilisers. It will have the capacity to process 82,000 tonnes per year of delivered waste (about 20,000 dry tonnes of digestible solids), representing about 10% of available organic waste in Sydney. Preliminary design work is also being carried out to include a 3.2 MW cogeneration unit, which will satisfy the requirements of the plant and export excess electricity into the grid.

The patented German BTA pre-treatment process already used in Europe and North America has been combined innovatively with Australian technology. The plant is scheduled for completion in October 2002 and should be in operation by the end of the year.

Wind energy

Wind energy is the fastest developing renewable energy source in Australia. This trend follows the growth in wind farms in other parts of the world. Europe is the leader in wind energy - since 1993 the market for wind turbines has grown by more than 40% per year. A wind turbine was first used to generate electricity in Denmark in 1891, while Australia's first commercial wind farm, at Ten Mile Lagoon near Esperance in Western Australia, has been operating for only about 20 years. Until recently, the share of wind energy in Australia's total energy consumption was very small, with just 72 MW installed by the end of 2001. The Australian Wind Energy Association (AusWEA) expects installed wind generation capacity to triple by 2002, with 500 MW of wind projects currently at various stages of planning and development. There is keen interest in developing wind farms in most states, and wind energy's share in electricity generation is set to increase markedly, with annual growth estimated to be about 25% from 1998-99 to 2019-20. This compares to a 2.3% annual growth rate for total energy consumption (ABARE 2001).

There are abundant wind energy resources worldwide, estimated to be about 53,000 terrawatt hours (TWh) or more than four times the world's entire electricity consumption of 14,396 TWh in 1998 (world electricity production is predicted to be 27,325 TWh by 2020). This was reported in Wind Force 10, a plan prepared by an international alliance to achieve 10% of the world's electricity from wind power by 2020. Greenpeace and AusWEA are members of this alliance, and have launched an initiative to build an Australian wind-power manufacturing industry and install 5,000 MW of wind energy capacity in Australia by 2010 - a 50-fold increase in capacity in 10 years. This target is equivalent to approximately 15,000 GWh of electricity each year, meeting the needs of 2.5 million average Australian homes (Blue Wind Energy 2002).

Why is there such impetus to grow wind energy capacity? Australia has among the best wind resources in the world and wind energy has become the cheapest renewable energy technology. Its current cost is only two to three cents more per kWh than the national electricity market pool prices, and this premium is reducing. Wind energy integrates well into the electricity grid, it is a proven technology and involves a short construction period. High quality modern wind generators are reliable, having an availability factor of 98%, and run during most hours of the year. This availability factor is beyond that of other electricity generating technologies.

Proponents of wind energy claim that it has many environmental advantages over other renewable sources. It is estimated by AusWEA that achieving the 5,000 MW target would cut Australia's total greenhouse gas emissions by more than 15 Mt or 3.3% of the nation's total 1999 emissions. Wind energy is an advancing technology and yields the most power per installed MW of capacity. It uses land resources sparingly, with generators and access roads occupying less than 1% of the area in a typical wind farm. In this respect a wind generator, using 36 square metres or 0.0036 hectares to produce 1.2 and 1.8 MkWh per year, compares favourably to solar cells requiring almost 400 times the area to produce the same amount of electricity. However, the relative land requirements of wind farms and solar installations depend on site-specific factors. While wind farms can be integrated with some land uses (e.g. grazing) as part of a multiple land use approach, they are not compatible with other land use options (e.g. farm forestry). Conversely, in some situations solar cells can be installed on buildings with no net requirement for land.

As well as producing zero pollutants (no waste products), wind energy generators have among the lowest energy 'payback periods'. The energy produced by a wind generator throughout its 25-year lifetime (in an average location) is 80 times larger than the amount of energy used to operate, dismantle and recycle it. In other words, on average, it takes only two to three months for a wind generator to recover all the energy required to build and dispose of it.

Other potential benefits of wind energy include enhancement of a clean and green image of the region and the potential for enrichment of habitat and re-establishment of indigenous vegetation. A better understanding of agriculturally impoverished flora and fauna species can be acquired through the process of assessing environmental impacts of wind farm proposals.

As with other energy sources, there are some adverse environmental impacts associated with the use of wind energy. While it is technically possible to have wind turbines on every hill, it would not be socially acceptable. Wind generators obviously have to be highly visible since they must be located in windy, open terrain to be effective. The loss of visual amenity is a critical issue in community acceptance of the high growth plans being proposed by wind energy developers, particularly in areas of great natural beauty such as those in coastal Victoria. Other issues are the impact on rare and endangered species such as the migratory orange-bellied parrots that are protected by Federal legislation, neighbours affected by noise and change in land values, radiation and interference with TV reception. One of the most critical issues is the lack of a coordinated approach on where future wind farms are going to be located.

Objections to some of these impacts are easier to overcome than others. Modern design and materials have greatly reduced the noise created by the turning blades, so that there is now less noise than the disturbance created by vehicle traffic along a highway. While older turbines with metal blades caused television interference in areas near the turbines, such interference from modern turbines is unlikely because many components formerly made of metal are now made from composites.

The impact on populations of birds and bats has been alleviated to a certain extent by developments in the turbines themselves - the bigger the turbine the better from the point of view of both birds and bats. Modern turbines are large, generally ranging from 660 kW to 1.5 MW, and turn quite slowly, making them far more visible and easy to avoid. The evolution of towers from a steel grid construction to a smooth steel tower has eliminated nesting opportunities for birds directly beneath the rotors, further reducing incidents of bird-strike. However it has been acknowledged that there has been a general lack of information on the migratory habits of Australian bird populations, and more work in this area is needed for the development of wind projects.

It is more difficult to overcome objections concerning land use and visual impact because most of these are subjective. Helping people understand the overall environmental good of wind generated electricity could counteract these concerns; so could a perception that better design, careful choice of turbines, and careful visualisation studies before siting could improve the visual impact of wind farms. There is now substantial experience in minimising the ecological impact of construction work in areas such as coastlines and mountains, or in offshore locations. Furthermore, it is possible to restore the surrounding landscape to its original state after construction, and to reuse, or completely remove, the foundations of wind generators at the end of their useful life.

Codrington is the first fully private investment (project cost was $30m) in a wind farm in Australia. It was Australia's second largest wind farm at the end of 2001 with a combined capacity of 18.2 MW from 14 turbines. The turbines are mounted on tubular towers 50 metres high. Power is produced at a wind speed of between 10.8 and 90 km/h, and is generated at 690 volts and stepped up to 66,000 volts with a transformer for connection to the electricity grid. The turbines are connected through underground cables before being connected to the local grid. Power generated will be purchased by the electricity retailer Origin Energy for use in its Ecosaver Green Power Product, with any surplus going towards meeting Origin Energy's liability under the MRET.

The site, located on the coast near Port Fairy in south-west Victoria, is owned by two farmers who lease access to Pacific Hydro. The turbines take up less than 1% of the area of the farm, which continues to be used for sheep and cattle grazing, and farm activities are unaffected.

Prior to construction, the project went through a comprehensive consultation process which examined local environmental impacts including birds, flora and fauna, Aboriginal cultural issues and local visual and noise studies, as well as its socioeconomic impacts.

The Codrington wind farm produces enough energy to supply more than 14,000 homes, and it is deemed to have the potential to abate the equivalent of up to 88,000 tonnes of carbon dioxide per year.

As a wind farm, Windy Hill is ideally located, with good exposure to prevailing winds and close vicinity to electricity transmission and major load centres. It consists of 20 turbines with a combined capacity of 12 MW, enough to power 3,500 homes. Each turbine is placed on a tubular tower which stands about 46 metres tall. The turbine blades are each 22 metres long and rotate at about 30 revolutions per minute.

The wind farm is built on privately owned farmland used predominantly for dairy and beef farming. Operating the wind farm has minimal impact on the farming activity.

An educational centre, the Power by Nature Centre, to provide detailed information on wind farms and other renewable energy technologies has been opened at Windy Hill. There are displays incorporating state of the art technology to allow visitors to see and interpret wind farm generation and activity as it happens.

The developer Stanwell Corporation Limited began investigating the site through a wind monitoring program in December 1998, and undertook additional studies and consultation on issues such as aesthetics, compatibility with telecommunication systems, noise and impact on wildlife.

Local firms and expertise have been used where possible during the construction and approximately 15% of the total cost of around $20m were spent on local fabrication and construction. Of the 17 contracting firms, 9 were based in Cairns or the Atherton Tablelands area. Long-term employment was made possible because local people will maintain the turbines.

Solar energy is Australia's largest energy source: the average amount of solar energy that falls on Australia is about 15,000 times the nation's energy use. In all parts of Australia, except southern Victoria and Tasmania, solar resources are good to very good. Sunlight can be used to generate electricity, provide hot water, and to heat, cool and light buildings.

The much higher cost of solar power installation relative to energy output, compared to other renewable as well as non-renewable energy sources, has been a major limiting factor in its uptake in Australia. A 1.5 kW solar power system has an area of about 11 square metres and generates around 1,800 kWh of electricity. Such a system typically costs around $20,000. Technological breakthroughs are, however, helping to bring this price down.

By its nature, solar energy is an intermittent and diffuse source. It is not available on cloudy days or at night, and it is not concentrated. Sunlight therefore has to be collected and/or converted for use. A range of commercially proven solar energy technologies is available:

Solar power systems convert sunlight into electricity, either directly via the photovoltaic effect, or indirectly by first converting the solar energy to heat or chemical energy. The simplest photovoltaic cells power watches and calculators and the like, while more complex systems can light houses and provide power to the electricity grid.

Concentrating solar power technologies use reflective materials such as mirrors to concentrate the sun's energy. This concentrated energy is then converted into electricity.

Solar hot water heaters use the sun to heat either water or a heat-transfer fluid in collectors. A typical system will reduce the need for conventional water heating by about two-thirds. High-temperature solar water heaters can provide energy-efficient hot water for large commercial and industrial facilities.

In Australia, solar power has traditionally been used in remote areas where electricity grid is not available. Such systems store electricity in batteries for use when the sun is not shining and are called stand-alone power systems. Telecommunication, for example, railway signalling systems, is a major market. Other industrial markets are also important, including navigational aids, cathodic protection, water pumping, street lighting, and remote refuelling (aviation) installations. Industry accounts for well over half the market. However solar power is now appearing more in urban areas, especially where government rebate (Australian Greenhouse Office's Photovoltaics Rebate Program launched in January 2000) and other assistance help to reduce the cost of installing solar energy systems to consumers.

Solar power systems give off no noise or pollution, making them ideal renewable energy suppliers. Their disadvantages, other than the high cost relative to energy output, lie in their relatively large structures and the reflective materials used by some technologies. These have implications for land use, aesthetics, and visual and other disturbance to the local community and to animals. Because of the advanced technologies and the materials involved, solar systems have relatively high payback period, in terms of the energy they produce and the energy required to produce and to operate them. It would seem that technological development would be the most important determinant in solar energy's uptake and in reducing its negative impacts.

Solar water heaters in Australia

In 1999, about 5% of Australian households used solar water heaters, with the majority of these systems (92%) using an electric booster. The highest proportion of hot water systems using solar energy occurred in the Northern Territory (44%) and Western Australia (20%) (ABS 1999). The average amount of hot water that can be gained from solar heating for home use ranges from 50% in southern states to more than 90% in northern Australia. However, energy (and money) saved by a properly sized system is roughly the same across Australia. The initial temperature of the water to be heated is lower in southern states, making energy supplied from the sun more ‘valuable’ in the heating process.

There are substantial environmental benefits with solar hot water systems. By replacing fossil fuel energy from burning coal or gas with solar energy, solar hot water systems can reduce the amount of greenhouse gas generated. As an example, if one were to replace an electric hot water system with a gas-boosted solar unit, one could reduce the amount of greenhouse gases produced by water heating by over 75%. The annual saving in greenhouse gas emissions would be around two tonnes, which is equivalent to driving a small car from Sydney to Perth and back again. Solar hot water systems may not always be the most environmentally friendly option for heating water, depending on the location and boosting method used. An electric-boosted solar water heater can produce more greenhouse gas emissions than a high-efficiency gas-only water heater in cooler climates where a solar system is more reliant on boosting. This means that replacing a gas water heater with an electric boosted solar water heater may create a detrimental effect on the environment (AGO 2002).

Case study

Solar power system on Lord Howe Island and Singleton solar farm (SEDA through the Australian Institute of Energy web site http://www.aie.it)

The SEDA owns a solar power system on Lord Howe Island. This 8 kW system is mounted on the airport roof and provides residents of this World Heritage-listed island with clean electricity. The islanders therefore avoid the high cost of generating electricity from diesel, as well as associated air and noise pollution. The Lord Howe Island solar power system is attractive and without adverse environmental impacts, and contributes significantly to the Island's power supplies.

The Singleton solar farm was commissioned in 1998 with the support of a grant from SEDA. Each year the 400 kW capacity farm produces 550,000 kWh of electricity used to supply public demand for Green Power. The clean solar power produced by the farm will eliminate the need to produce 550 tonnes of carbon dioxide each year from the traditional means of electricity production. The Singleton solar farm has been warmly welcomed by the community, as much for the interest it creates as for the environmental benefits it will bring for many years to come.

Wave power, tidal energy and geothermal energy

Wave power is sourced from winds blowing on oceans, tidal energy by the gravitational pull of the moon on the ocean, and geothermal energy is heat from the earth. These renewable energy resources are clean and sustainable, and all are abundant in Australia. However they are at early stages of research and development, and it may be many years before they become commercially viable.

Australian wave power developer Energetech's wave power system is powered by an oscillating water column driving air back and forth through a turbine mounted on a shoreline structure such as breakwaters. The first 300 kW Energetech system is under construction on the breakwater at Port Kembla. Wave power has enormous potential, with studies suggesting that many billions of dollars could be invested in this form of electricity generation over the next two decades. Energetech's shore-mounted system driving the novel Denniss Turbine is well regarded by international observers as having the best potential for economic wave energy development (Australian Energy News, March 2002).

The future of renewable energy

Australian governments are strongly supporting the surge in renewable energy development. While renewable energy's share of total energy consumption will remain small relative to non-renewable sources for a long time to come, its capacity is expanding enormously from a small base.

Continuing government funding and support in providing information and practical assistance will facilitate the renewable energy growth. The recent release of the Wind Energy Handbook and guidelines for preparation of an environment impact statement for wind farms are signs of increasing inter-governmental support, beginning at the planning phase for these projects. Businesses are increasingly aware of the economic potentials of renewable energies and are actively building industry capacities and exploring export opportunities. Households are contributing by indicating their preference for 'green electricity' through participating in the Green Power program and installing solar power in their dwellings.

Each renewable energy source has unique characteristics, making them suited to a wide range of purposes, sites and situations. In general they are all better for the environment than non-renewable energy sources, and technological advances will continue to assist in reducing the negative impacts.

Australian Greenhouse Office and Australian Wind Energy Association 2002, Best Practice Guidelines for Implementation of Wind Energy Projects in Australia.Bioenergy Australia, Conference notes, December 2000.

OECD/IEA 2002, IEA Wind Energy 2001 Annual Report, National Activities for Australia, compiled by Robert Stewart, in agreement with Australian Wind Energy Association.

Redding Energy Management in association with RMIT Energy and Environmental Management Group, submitted to Australian Greenhouse Office, January 1999,2% Renewables Target in Power Supplies, Potential for Australian Capacity to Expand to Meet the Target.

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